In recent years, in the field of toners for electrophotography, with the progress of electrophotographic systems, it has been demanded to develop toners adaptable for high image quality and high copying or printing speed. From the viewpoint of the high image quality, the toners have been required to have a small particle size. Thus, there have been disclosed processes for producing a so-called chemical toner by a chemical method such as a suspension polymerization method, an emulsion polymerization method and a dissolution suspension method in place of the conventional melt-kneading method. Further, from the viewpoint of the high copying or printing speed, there has been reported a chemical toner to which a releasing agent is internally added in order to improve low-temperature fusing properties thereof.
For example, JP 2010-169702A discloses a toner including core particles produced by aggregating at least resin particles, colorant particles and wax particles, in which a dispersant used in a dispersion of the wax particles contains a polypropylene glycol ethyleneoxide adduct. JP 2010-169702A also describes that the problem that the wax particles or the colorant particles are not aggregated with the other components of the core particles in an aqueous system and therefore remain unincorporated into the core particles can be solved, so that it is possible to produce toner particles having a narrow particle size distribution and a small particle size.
JP 2012-128024A discloses a process for producing a toner including the steps of mixing resin particles containing a polyester as a main component, releasing agent particles containing a wax and a polyester resin having a specific softening point at a specific weight ratio, and an aggregating agent in an aqueous medium to obtain aggregated particles (1); mixing the aggregated particles (1) with polyester-containing resin particles serving as a shell to obtain aggregated particles (2); and coalescing the particles constituting the aggregated particles (2) to obtain core/shell particles. In JP 2012-128024A, it is described that the toner obtained by the production process is excellent in low-temperature fusing properties and heat-resistant storage properties.
JP 2014-89442A discloses a process for producing a toner for electrophotography which is capable of suppressing isolation of a wax from a resin binder as well as exposure of the wax onto the surface of respective toner particles in the step of obtaining coalesced particles upon production of the toner, reducing the amount of a fine powder included in the toner, and providing the toner that is excellent in low-temperature fusing properties and anti-hot offset properties. In JP 2014-89442A, it is also described that in the aforementioned process, a water dispersion of releasing agent particles obtained by mixing and emulsifying the wax with an emulsion of a resin having a specific acid value and an oxazoline group-containing polymer is mixed with a water dispersion of resin particles including the resin binder containing a carboxy group, and the resulting mixture is aggregated and then coalesced to obtain coalesced particles.